Fluid meter



May 14, i929.

W. H. G. FURNIVALL. ET AL FLUTD MET ER Filed July 7, 1925 Patented May 14, 1929.

UNITED STATES PATENT OFFICE.

WILLIAM HENRY GRAHAM FURNIVAI'L, DAVID BERTI-IA MCIJAREN, AND EDGAR JACOB LASCI-IINGER, OIE' JOHANNESBURG, SOUTH AFRICA.

`:FLUID METER.

Application filed .T uly 7, 1925, Serial No. 42,006, and in Great Britain November 10, 1924.

The present invention relates to fluid meters of the kind in which the flowing fluid displaces a pivoted gate tending to close against the flow; and in which a shield curved in the direction of the path of the free edge of the gate provides in itself, or fornis with said free edge of the gate, a gate controlled orice for the :fluid which varies in area according to the displacement of the gatefroin lo its zero position.

rThe purpose of the invention to provide a nieter of this kind having a gravity gate and an orifice such that the displacement of the gate is directly proportional to the rate of flow of the fluid.

The invention is illustrated in the accoinpanying drawings in which, y

Fig. I shows a meter sectioned on I-I Fig. II, the gate being partly open.

Fig. II is a section of the saine on II-II Fig. I, with the gate shut.

Iii g. III is a similar' view to Fig. I but showing a modification.

Fig. IV is a developed view of the slotted shield of Fig. III.

In the dra-Wings l indicates the meter casing providing a substantially straight fluid passage indi cated by 2, 3. The gate l pivoted to swing about the axis 5, and at no flow hangs across the line of flow of the fluid. A stop G liinits its upward movement 'when raised by the flow of fluid. It is preferred to provide seat 7 against which the gate closes at no flow and so to arrange the centre of gravity C, of the gate that at no flow a coinponent of its weight remains effective to hold it against the seat and provide an initial resistance to its movement. S is the shield which is arranged adjacent to the path of nioveinent 9 of the free edge 10 of the gate.

In the construction shown in Figs. I and II the shield curves away from the path 9, and the variable orifice for the fluid is the area I between the free edge 10 of the gate and the shield, which area becoines progressive ly greater as the gate swings upwards, and so passes increasing quantities of fluid per unit of tinle. 'Ihe fluid flows away over the free end 11 of the shield.

In. the modification .shown in Fig. III the shield conforms closely to the path 9. The orifice is formed by the slot 12 in the shield, which slot is progressively uncovered by the CIK gate as it swings upwards; the fluid flowing through the part of the orifice thus uncovered. Fig. IV shows that the width t of the slot decreases from its lower end 13 towards its upper end lll.

In both constructions the area, or utilized area, of the orifice corresponding' to any an gular position of the gate is such that the flow of fluid :is directly proportional to the displacement of the gate from its closed position. A measuring pointer 15 or the like inay accordingly be mounted directly on the spindle 16 of the gate and co-operate with a dial 17, a'chart or the like, having equally spaced divisions.

Applicants have computed the following general formula for calculating the area of the orifice at, any position of the gate, which is necessary to causethc displacement, from Zero, of the gate in that position, to be directly proportional to the flow of fluid in that position, viz l A (orifice area in square inches) J M Grasa-N (l) In this expression Mis the value, in degrees, of the actual angular displacement of the gate from its closed position. N is the value, in degrees, of the angular displacement of the centre of gravity of the gate frein the vertical line through the axis of the gate. N thus equals M-tO, where O the angle of lead, or in other words the angle through which the centre of gravity of the gate is displaced froin the vertical line through the axis of the gate, when the gate is closed. It will be evident from the formula that the essential relationship between the area of the orifice and the angular displacement of the gate is that the area varies directly as angle M and inversely as the vsquare root of sine N.

rlhe factor o represents the co-eflicient of discharge for the orifice, and inay usually be regarded as a constant. Actually its value varies slightly with the area of the orifice; and when particular accuracy is necessary, it is determined experimentally.

The value of the factor J for the Fig. I construction is found by dividing the inaxiinuin desired flow of fluid (measured, in the case of compressed air, in pounds per minute) by the maximum desired displacement of the gate in degree-s. The-ligure thus obtained multiplied by gives the value of J for the Fig. III

construction.

K is a constant represented by the expression z n QgWLY K 144141) in which g=accelerat1on due-t0 gravity 1n feet per sec-- lond per second.

lV: weight of gate in pounds. .L=d1stance 1n inches from centre or gate '71.:191 less the fluid pressure at the outgoing side of the gate (i. e. at 3) in lbs. per square inch. Qluid flowing in'lbs. per second.V

` R gas constant.

T: absolute temperature. f

The known formula for low through an orilice is RT=speciic weight of the incoming Huid Y, in lbs. per cubic foot to which the symbol Yis assigned above, so that the equation becomes :A i1 Q C 14.4 .(10) From the known theory of the balance of couples there is derived hapvLxsinN (11) from which l ,as 'N/gvS-f N 12) Substituting this value of Jh in equation (10) gives Indicating by the symbol K, as explained above, brings the equation to the form Q=Ac KJsv (14) But as it is a condition that the angle of movement M of the gate shall bc proportional to the rate of flow Q.

Q=JM (15)' Equating the two values of Q from 14 and l5 The general equa-tion (l) given above is applicable to either the Fig. I or the Fig. 1V construction. From it the orifice areas corresponding to a number of diilerent values of the angle of displacement, M, can be determined and thus the form of the whole oriiice can be arrived at.

In practice it islnore convenient to use modifications of this formula suitable for the specilic form of the invention which is to be, constructed. Thus in the Fig. I form of the invention, the orilice is always a rectangle and its area is Bb, Where b is the breadth and B is the width, both in inches. The expression Bb may accordingly be equated to the general expression for area thus- As the breadth of the orifice remains constant in this case, Equation (3) gives the values of the varying width l, correslmndin g to different values of M. By calculating a number of values of B the proper curvature of. the shield g in Fig. I is arrived at. In the ease of the Fig. III construction, the variable to be calculated is the width t of the slot for the dill'erent values of M. An equation (8 below) for this purpose is obtained as follows, using a new factor F which represents tbe distance, in inches, from the axis of the gate to the free edge S of the same.

The general equation angles M and N are expressed in terms of arc to radius unity.

d M :s w/sin N'M-Mdy/sin N w/sin N sin N (i1/sin N (Sm N) Zw/sin N formula (4L) becomes Y Since N (M+ O) and O is constant cZN=aZM p (6) In terms of its width t and the factor F, the area of' the slot in F ig. IV is given by A ftFaM aa Fair (7) Combing Equations 5, 6 and 7 and convert1ng,so as to express M 1n degrees, gives J 1r/[ 2eme/Sin N 2 180 COL N) (8) By calculating the width t for a number of' different angles M, the form of the slot t is obtained.

TNe claim l. A fluid meter comprising a casing, a gate pivoted within the casing to be swung up about an axis and against gravity by the flow oi fluid through the meter, a shield curved in the general direction of the path of the iree edge of the gate, said free edge of the gate and the shield being shaped to define an orilice for the flow of fluid, the area of which orifice varies with the displacement of the gate and is a function both of the angular displacement of the gate and the angular displacement of the center of gravity of the gate, from a vertical position below the gate pivot axis, and flow measuring means comprising' a member connected to the gate to `move therewith and adapted to be used as an index of the extent of its movement.

2. A fluid meter comprising a casing providing a passage for the flow of fluid, a pivoted gate adapted to hang at no flow across said passage and to be swung upwards against gravity by the flow, and a shield curved in the direction of the path of the free edge ot' the gate, said free edge of the gate and the shield being shaped to define an orifice for the flow oi fiuid, the area of which orifice corresponding to any angular position of the gate varies directly as the angle of displaceand so that (in inches) ment of the gate from its no flow position and inversely as the square root of the sine of the angle of displacement of the centre of gravity of the gate from a vertical line through the axis of the gate.

A fluid meter comprising a casingtpro- `viding a passage for the flow of fluid, a pivoted gate adapted to hang at no flow across the passage and to be swung upwards against gravity .by the flow, and a shield curved in the general direction of the path of the free edge of the gate; but diver-ging therefrom towards its upper part in such a manner that the space between said edge of the gate and the shieldforms an orifice of which the area corresponding to an",7 angular position oi' the varies directly as the angle of displacement of the gate from its no flow position and inversely as the square root of the sine of the an gle of displacement of the centre of gravity of the gate from a vertical line through the axis ofthe gate.

4. A fluid meter coniprising a easing pro-` viding a passage for the flow of fluid, a pivoted gate adapted to hang at no flow across the passage and to be swung upwards against gravity by the flow, and a shield curved in the general direction of the path of the free edge oi' the gate but diverging therefrom towards its upper part in such a manner that the space between'said edge of the gate and the shield forms a rectangular orifice oi which the breadth varies directly as the angle of displacement of the gate from its no flow position and inversely as the square root of the sine oi the angle of displacement of the centre oi. gravity of the gate from a vertical line through the axis of the gate.

5. A fluid meter comprising a casing, a gate pivoted within the casing to be swung up about an axis and against gravity by the flow of fluid through. the meter, a shield curved in the general direction of the path of the free edge oil the gate, said 'free edge of the gate and the shield being shaped to define an orilice for the How of fluid, the area of which orilice varies with the displacement of the gate and is a function both of the angular displacement of the gate and the angular displacement of the center of gravity oit the gate, from a vertical position below the gate pivot axis, and flow measuring means comprising a member connected to the gate to move therewith .in con'ibination with a measuring scale, the said member adapted to indicate on said scale the extent ol movement of said gate.

Signed at Johanncsbiiirg, 'llransvaal Province, Union of South Africa, this 3rd day of June, 192V.

WILLIAM HENRY GRAHAM FURNIVALL.

DAVID BERTHA McLAREN.

EDGAR JACOB LASCHINGER. 

